Device for the production of homogenous microwave plasma

ABSTRACT

A device for generating microwave plasmas and having a microwave generator, a chamber feeding microwaves, and a plasma chamber with receptacles, if appropriate, is proposed, the chamber being of cylindrical construction. The plasma chamber preferably comprises the cylindrical chamber completely or partially. Coupling points are arranged in the common wall, preferably as slot couplers.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the production of a homogenous plasma.More specifically, the present invention relates to a device that usesmicrowaves for the production of homogenous plasma.

2. Description of the Prior Art

Various types of plasmas are generated using a wide variety of methodsand devices. Plasma treatment is used, for example, for coating,cleaning, modifying and etching substrates, for treating medicalimplants, for inverting gases and in technology for purifying wastegases. The geometry of the workpieces to be treated ranges from flatsubstrates, fibers and webs, to any configuration of shaped articles.The size of the plasma chamber, and thus of the workpieces is limited.Materials in web form and fiber bundles can be processed only withdifficulty.

Known devices have, for example, outer rings which can be constructed asa resonator. To feed the microwaves, use is made, inter alia, ofwaveguides and coaxial cables and, inter alia, of antennas, for exampleslots, as coupling points in the wall of the plasma chamber.

A disadvantage of the known devices are the formations ofinhomogeneities in the in the plasma, particularly at high pressures andin relatively large plasma chambers and/or substrates.

The task therefore existed of generating a homogenous plasma andrendering possible homogenous plasma treatment.

SUMMARY OF THE INVENTION

It is proposed according to the invention to introduce the microwaveshomogenously into the plasma chamber serving the purpose of processingvia a cylindrical chamber and via coupling points in the cylindricalwall of this chamber. The plasma chamber is then to be constructed onthe outside completely or partially covering the cylindrical wall of thechamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a device for the production ofhomogenous microwave plasma.

FIG. 2a is a lateral view of the developments of the lateral surfaces ofthe cylindrical chamber of the device as shown in FIG. 1 showingcoupling points in the wall with the plasma chamber.

FIG. 2b is a lateral view of the developments of the lateral surfaces ofthe cylindrical chamber of the device as shown in FIG. 1 showingazimuthal slot couplers with a spacing of equal phase.

FIG. 2c is a lateral view of the developments of the lateral surfaces ofthe cylindrical chamber of the device as shown in FIG. 1 showing twopairs of azimuthal slot couplers with a spacing which are displacedrelative to one another.

FIG. 2d is a lateral view of the developments of the lateral surfaces ofthe cylindrical chamber of the device as shown in FIG. 1 showing twopails of rows of slot couplers having opposing directions of tilt.

FIG. 2e is a lateral view of the developments of the lateral surfaces ofthe cylindrical chamber of the device as shown in FIG. 1 showing aplurality of continuous coupling slots which run parallel to the x-axis.

FIG. 2f is a lateral view of the developments of the lateral surfaces ofthe cylindrical chamber of the device as shown in FIG. 1 showing aplurality of interrupted coupling slots which run parallel to thex-axis.

FIG. 3a is a perspective view of a device for the production ofhomogenous microwave plasma in the preferred construction as an annularresonator having a rectangular cross-section, wherein the microwavelaunching is performed via the short rectangular side.

FIG. 3b is a perspective view of a device for the production ofhomogenous microwave plasma in the preferred construction as an annularresonator having a rectangular cross-section, wherein the microwavelaunching is performed via the long rectangular side.

FIG. 4a is a perspective view of a device for the production ofhomogenous microwave plasma wherein the plasma chamber is constructed asa 180° segment of a cylinder and wherein the microwave launching isperformed via the short rectangular side.

FIG. 4b is a perspective view of a device for the production ofhomogenous microwave plasma wherein the plasma chamber is constructed asa 180°0 segment of a cylinder and wherein the microwave launching isperformed via the long rectangular side.

FIG. 5 is a perspective view of a device for the production ofhomogenous microwave plasma wherein the plasma chamber is of equallength as the feeding chamber and is constructed as a 180° segment of acylinder.

FIG. 6 is a perspective view of a device for the production ofhomogenous microwave plasma showing a substrate located in the plasmachamber.

FIG. 7 is a perspective view of two devices arranged in sequential orderfor treating a web-shaped substrate.

FIG. 8 is a cross section of a perspective view of a device for thecontinuous processing of tubes which are guided continuously through theplasma chamber.

FIG. 9 is a perspective view of a device having coaxial chambers inbeing geometrically adapted to accommodate substrates.

FIG. 10 is a side view of the device as shown in FIG. 1, taken along thez-axis.

FIG. 11 is a cross section of the device as shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, the subject matter of the presentinvention, as shown in FIG. 1, is a device for generating microwaveplasmas and referred to generally at numeral 10. Device 10 comprises amicrowave generator 12, a feeding chamber 14, a plasma chamber 16, aplurality of coupling points 18 in the wall 15 between the feedingchamber 14 and plasma chamber 16, as well as, if appropriate, aplurality of receptacles 20, characterized in that the microwave feedingchamber 14 is of a cylindrical design. Device 10 further comprisesfeeding chamber end faces 22 a, b and plasma chamber end faces 24 a, b.Feeding chamber end faces 22 a, b and plasma chamber end faces 24 a, blie in the same vertical plane in this case. Cylindrical feeding chamber14 is surrounded by the plasma chamber 16 with a microwave generator 12in one end face 22 a of the feeding chamber 14.

The feeding chamber end faces 22 a, b are preferably not covered by theplasma chamber 16. The plasma chamber 16 completely or partially coversthe cylindrical wall of the feeding chamber 14.

The common wall 15 between the feeding chamber 14 and the plasma chamber16 is preferably to be constructed completely, partially orsubstantially in a cylindrical fashion. The configuration of the outerwall 17 of the plasma chamber 16 is of cylindrical or arbitraryconfiguration, for example, adapted to the type of processing beingused. As a resonator, the plasma chamber 16 can be constructed, forexample, as a resonator of coaxial, rectangular or annular shape. As anannular resonator, the plasma chamber 16 can, given a rectangular crosssection, form the common wall 15 with the feeding chamber 14 with theshort or long side. The plasma chamber 16 can also be constructed as asegment of the said shapes.

The plasma chamber 16 and the cylindrically shaped feeding chamber 14preferably have a common preferred direction and, in the simplest, muchpreferred case, a common z-axis. It is also preferred for the feedingchamber 14 to be of a rotational symmetrical construction, at least inparts, particularly the parts near the feeding chamber end faces 22 a, band plasma chamber end faces 24 a, b. Two tubes arranged inside oneanother and having a common z-axis are structurally the simplest,surprising and much preferred arrangement of the feeding chamber 14 andplasma chamber 16.

The feeding chamber 14 and plasma chamber 16 can be constructed with thesame or different lengths along the preferred direction or axis.

The cylindrical shape and the simple geometrical configuration of thefeeding chamber 14 permits improved uniformity of the microwavelaunching and simple construction of the feeding chamber 14 and plasmachamber 16 as resonators. The cylindrical shape of the feeding chamber14 also permits a previously impossible variation, variability andadjustability of the configuration and effectiveness of the feedingchamber 14 and also of the plasma chamber 16. For this purpose, at leastone of the feeding chamber end faces 22 a, b can be arranged moveablyand/or displaceably. Furthermore, at least one of the plasma chamber endfaces 24 a, b can be arranged moveably and/or displaceably. Displacementin the preferred direction and/or rotation of the feeding chamber endfaces 22 a, b and plasma chamber and faces 24 a, b is possible in aparticularly simple way. For this purpose, the feeding chamber end faces22 a, b and plasma chamber end faces 24 a, b have exciting holders, tubestubs or the like at the cylinder wall 17. The tube stubs can havecutouts and be constructed over small or substantial parts of thecylinder wall 17 in a fashion bearing against the cylinder wall 17. Thecoupling points 18 can then be arranged variably, moveably and settablyand be configured so that they can be covered or be switched in byopening. The cylinder wall 17 is then thereby completely or partially oftwo-fold or three-fold structure.

Moveable coupling points 18 can be arranged moveably with the aid of thefeeding chamber end faces 22 a, b and plasma chamber end faces 24 a, bor by means of handles, for example, independently of the feedingchamber end faces 22 a, b and plasma chamber end faces 24 a, b. In manycases, the feeding chamber 14 preferably has an ideal or substantiallycylindrical shape and azimuthal slots, for example, as coupling points18. In other words, azimuthal slots, as referenced at numeral 26 inFIGS. 2a-2 f, are just one specific example of coupling points 18. Thefeeding chamber end faces 22 a, b and plasma chamber end faces 24 a, bare then circular, or the contact surface with the cylinder wall is acircle and the slots, which can be switched in and out, can be movedthrough the feeding chamber end faces 22 a, b and plasma chamber endfaces 24 a, b and/or from the outside.

The feeding chamber 14 can also deviate from the ideal shape of acylinder, For example, feeding chamber 14 can have an elliptical orangular cross section or even a triangular to hexagonal cross section,completely or partially. A shape curing around the z-direction is alsopossible. The cylinder of the feeding chamber 14 can be curved. Thefeeding chamber end faces 22 a, b and plasma chamber end faces 24 a, bcan touch one another or be eliminated and the feeding chamber 14 canhave an annularly closed structure. The shape of the feeding chamber 14stretched linearly along the z-direction is much preferred.

The plasma chamber 16 can have a feed for gases and a device for theevacuation of gases. The device of the invention can be used in aversatile fashion, but the treatment of materials in web form and ofvirtually arbitrary width is possible, in particular.

In order to generate a vacuum, plasma chamber 16 can include areceptacle 20 which consists completely or partially of a dielectricmaterial with preferably low dielectric losses, for example silica glassor aluminum oxide ceramic. In the case of the construction of plasmachamber 16 as a coaxial resonator, receptacle 20 (FIGS. 10 and 11) canbe designed with the aid of a dielectric tube 21 (FIGS. 10 and 11), forexample made from silica glass, which is pushed over the cylinderresonator. In this case, dielectric tube 21 forms the vacuum receptacle20 together with the outer conductor of the coaxial resonator and thefeeding chamber end faces 22 a, b thereof. In the case when the deviceis operated at higher pressures, for example atmosphere, the receptacle20 prevents the formation of a plasma at the coupling points 18 a, band/or in the feeding cylindrical chamber 14, the supply lead thereof,or else on the microwave generator 12 itself However, by introducingdielectric material (i.e., dielectric tube 21), the plasma region of thedevice can likewise be specifically limited to the desired regions.Thus, for example, by cladding the region around the coupling point andthe coupling points 18 a, b themselves with dielectric material, it ispossible to prevent the production of a plasma in this region.

If [the] plasma chamber 16 is designed as a coaxial resonator, it ispreferably constructed as a TEM resonator. However, other modes such as,for example, TE modes or TM modes are also possible. In a case oftreatment of materials in web form, such as, for example, plastic ormaterial webs, the material to be treated can be fed and/or removedthrough slots in the outer conductor of the TEM coaxial resonator, forexample along the z-axis, without being coupled outwards owing to thismicrowave power. Designing the cylindrical plasma chamber 16 to be fedas a TM010 resonator with azimuthal slot couplers 66 (FIG. 9) ispreferred in this case. It is preferred that the spacing of the slotcouplers 66 (FIG. 9) in the z-direction is in this case a wavelength ofthe microwave used. Likewise possible are a plurality of slots 66 (FIG.9) which are distributed around the circumference of the cylinderresonator and tilted out of the azimuthal direction in the direction ofthe z-axis by, for example, 45 degrees. It is also possible in this caseto design an arrangement of rows of slots 66 (FIG. 9) at a spacing orhalf the wavelength, in which case the tilting direction of the slots 66(FIG. 9) should be opposite from one row of slots to the next.

It is also possible to construct the plasma chamber 16 as a feedingchamber and the feeding chamber 14 as a plasma chamber.

Moveable coupling points 18 a, b and/or feeding chamber end faces 22 a,b lead, if appropriate, to assigning the function of conduction to theouter plasma chamber 16 and the function of the plasma chamber 16 to theinner feeding chamber 14.

Launching the microwaves into the plasma source can be performed usingthe known tuneable supply leads via a wall of the chambers; preferablyvia an end wall or chamber wall, the tuning of the plasma source beingperformed completely or partially by setting in and through a chamberwall. The tuning can also be performed via the known tuning elements.

All the parts of the devices can be present in multiple fashion.

Turning now to FIGS. 2a-2 f, the developments of the lateral surfaces ofthe cylindrical feeding chamber 14 with coupling points 18 in the wallwith the plasma chamber 16 are shown. FIG. 2a shows a plurality ofcoupling points 18 in a more specific form of azimuthally circulatingslot couplers 26 with a spacing D of preferably one or half a wavelengthat resonance. FIG. 2b shows a plurality of azimuthal slot couplers 26with a spacing D of equal phase, which cover the circumference of thecylindrical surface only partially. FIG. 2c shows two pain of azimuthalslot couplers 26 with a spacing D which are displaced relative to oneanother by D′ of, for example, a quarter wavelength. By mechanicallydisplacing the feeding chamber end faces 22 a, b and/or the plasmachamber end faces 24 a, b by D′ in the direction of the z-axis, couplingis produced by both or only one pair of slots 26, The slots 26 need notalso be displaced. In the case of only one slot row, feeding chamber endfaces 22 a, b, plasma chamber end faces 24 a, b and slots 26 must bedisplaced in order to achieve the homogenization. A slot pair 26 isconnected to the plasma chamber end face 24 a, b with the aid of aholder and is displaced in the z-direction by the movement thereof. Thefeeding chamber end faces 22 a, b are displaced until resonance isachieved. FIG. 2d shows two pairs of rows of slot couplers 26 havingopposing directions of tilt with a spacing of respectively D and half ofthe spacing D from one another, as a result of which use is made ofco-phasal launching into the plasma chamber 16. In other words, theopposite flow direction of the wall flows through opposing coupling ofthe rows of slots 26 at a spacing of, for example, half the resonatorwavelength. Additional rows of slots 26 at a spacing of, for example, aquarter wavelength are possible. Rows of slots 26 can be displaced, asshown in FIG. 2c.

FIGS. 2e and 2 f show a plurality of coupling slots 26 which runparallel to the z-axis and can be changed, for example, by rotatingand/or displacing the plasma chamber end face 24 a, b. The slots 26 areinterrupted in FIG. 2f Other coupling elements can be used instead ofslots 26.

FIG. 3 shows a device having a plasma chamber 16 in the preferredconstruction as an annular resonator of rectangular cross section, themicrowave launching from feeding chamber 14 and being performed via ashort rectangular side 28 or a long rectangular side 30.

FIG. 4 is the same as FIG. 3, but the feeding chamber 14 is enclosed bya plasma chamber 16 which is constructed as a 180° cylinder segment.

FIG. 5 shows the feeding chamber 14, enclosed by the plasma chamber 16.

The plasma chamber 16 and feeding chamber 14 are constructed with thesame length in the z-direction and are constructed as a 180° segment.

FIG. 6 shows a long feeding chamber 14 enclosed by a plasma chamber 16which is constructed to be longer than a 180° segment and through whicha web-shaped substrate 32, which is to be treated, is moved continuouslythrough the substrate entry slot 34. The substrate exit slot is notrepresented.

FIG. 7 shows two devices 40 a, b for treating a web-shaped substrate 32which use optionally identical or different methods, the web-shapedsubstrate 32 being guided sequentially through the respective substrateentry slots 42 and 44.

FIG. 8 shows a device for the continuous processing of tubes 46 whichare guided continuously through a plurality of annular slots 48 of theplasma chamber 16 at tight angles to the plane of the drawing of FIG. 8athrough annular slots 48. The tube 46 to be processed always has thesame spacing from the coupling elements (not shown) of the annularfeeding chamber 14, whose center line 50 is produced in the form of acircle by imaginary constant curvature of the cylindrical axis. In FIG.8a, the feeding chamber 14 has a circular cross section, but it can alsohave a curved oval cross section or else an angular one. FIG. 8b shows asection through the devices in accordance with the line of section AB inFIG. 8a. The plasma chamber 16 is arranged as a 180° segment of acircular ring outside the ring of the feeding chamber 14, such that theouter 180° segment of the feeding chamber 14 is provided with couplingelements (not shown). The semicircle of the cross section of the plasmachamber 16 can also be constructed as a rectangle.

FIG. 9 shows an alternative device 60 having coaxial chambers 62 and 64,which follow a curved axis (not shown) in being geometrically adapted toaccommodate substrates 32. In the plane of the azimuthal slot couplers66, the cross sections can be circular or, for example, elliptical andof constant or non-constant diameter along the curved axis.

FIGS. 10 and 11 show a side view and a cross-section of device 10,respectively. As explained above, in order to generate a vacuum, plasmachamber 16 can include receptacle 20 which consists completely orpartially of a dielectric material with preferably low dielectriclosses, for example silica glass or aluminum oxide ceramic, In the caseof the construction of plasma chamber 16 as a coaxial resonator,receptacle 20 can be designed with the aid of dielectric tube 21, forexample made from silica glass, which is pushed over the cylinderresonator. In this case, dielectric tube 21 forms the vacuum receptacle20 together with the outer conductor of the coaxial resonator and thefeeding chamber end faces 22 a, b thereof (FIG. 1).

The invention has been described in detail, with particular emphasishaving been placed on the preferred embodiments, but variations andmodifications within the spirit and scope of the invention may occur tothose skilled in the art to which it pertains.

What is claimed is:
 1. A device for generating microwave plasmas, said device comprising: a microwave generator; a microwave feeding chamber of cylindrical design; a plasma chamber; a common wall between said feeding chamber and said plasma chamber; and a plurality of coupling points which are located within said wall and through which the microwave energy is conveyed from said feeding chamber into said plasma chamber; wherein the plasma chamber and the feeding chamber being the same length.
 2. A device for generating microwave plasmas, said device comprising: a microwave generator; a microwave feeding chamber of cylindrical design; a plasma chamber; a common wall between said feeding chamber and said plasma chamber; and a plurality of coupling points which are located within said wall and through which the microwave energy is conveyed from said feeding chamber into said plasma chamber; wherein said feeding chamber comprises end faces, and wherein at least one of said end faces is adjustable.
 3. The device of claim 2 wherein said plasma chamber comprises end faces, and wherein at least one of said end faces of said plasma chamber is also adjustable.
 4. The device of claim 2 wherein said end face(s) is/are adjustable by rotation.
 5. The device of claim 2 wherein said end face(s) is/are adjustable by shifting along a common axis.
 6. A device for generating microwave plasmas, said device comprising: a microwave generator; a microwave feeding chamber of cylindrical design; a plasma chamber; a common wall between said feeding chamber and said plasma chamber; and a plurality of coupling points which are located within said wall and through which the microwave energy is conveyed from said feeding chamber into said plasma chamber; wherein said plasma chamber comprises end faces, and wherein at least one of the end faces of the plasma chamber is adjustable.
 7. The device of claim 6 wherein said end face(s) is/are adjustable by rotation.
 8. The device of claim 6 wherein said end face(s) is/are adjustable by shifting along a common axis.
 9. A device for generating microwave plasmas, said device comprising: a microwave generator; a microwave feeding chamber of cylindrical design; a plasma chamber; a common wall between said feeding chamber and said plasma chamber; and a plurality of coupling points which are located within said wall and through which the microwave energy is conveyed from said feeding chamber into said plasma chamber; wherein said wall is, at least in part, constructed from the group consisting of a double wall, a threefold wall and a multiple wall, and wherein the wall with the coupling points is arranged displaceably.
 10. The device of claim 9 wherein the wall with coupling points is arranged rotatably.
 11. A device for generating microwave plasmas, said device comprising: a microwave generator; a microwave feeding chamber of cylindrical design; a plasma chamber; a common wall between said feeding chamber and said plasma chamber; and a plurality of coupling points which are located within said wall and through which the microwave energy is conveyed from said feeding chamber into said plasma chamber; wherein said wall is, at least in part, constructed as a double, threefold or multiple wall, and wherein the wall with the coupling points is arranged rotatably.
 12. A device for generating microwave plasmas, said device comprising: a microwave generator; a microwave feeding chamber of cylindrical design; a plasma chamber; a common wall between said feeding chamber and said plasma chamber; and a plurality of coupling points which are located within said wall and through which the microwave energy is conveyed from said feeding chamber into said plasma chamber, and wherein said coupling points are adjustable or movable.
 13. The device of claim 12 wherein at least one of said chambers comprises at least one adjustable end face which is provided with means by which said coupling points can be adjusted.
 14. A device for generating microwave plasmas, said device comprising: a microwave generator; a microwave feeding chamber of cylindrical design; a plasma chamber; a common wall between said feeding chamber and said plasma chamber; and a plurality of coupling points which are located within said wall and through which the microwave energy is conveyed from said feeding chamber into said plasma chamber; wherein said wall is, at least in part, constructed as a double, threefold or multiple wall, and wherein at least one of these walls is arranged displaceably.
 15. A device for generating microwave plasmas, said device comprising: a microwave generator; a microwave feeding chamber of cylindrical design; a plasma chamber; a common wall between said feeding chamber and said plasma chamber; and a plurality of coupling points which are located within said wall and through which the microwave energy is conveyed from said feeding chamber into said plasma chamber, and wherein said wall is, at least in part, constructed as a double, threefold or multiple wall, and wherein at least one of these walls is arranged rotatably.
 16. A device for generating microwave plasmas, said device comprising: a microwave generator; a microwave feeding chamber of cylindrical design; a plasma chamber; a common wall between said feeding chamber and said plasma chamber; and a plurality of coupling points which are located within said wall and through which the microwave energy is conveyed from said feeding chamber into said plasma chamber; the plasma chamber and the feeding chamber having a common direction and being the same length.
 17. The device of claim 16 wherein said common direction is the direction in the z axis.
 18. The device of claim 16 wherein the plasma chamber and the feeding chamber are of different lengths.
 19. A device for generating microwave plasmas, said device comprising: a microwave generator; a microwave feeding chamber of cylindrical design; a plasma chamber; a common wall between said feeding chamber and said plasma chamber; and a plurality of coupling points which are located within said wall and through which the microwave energy is conveyed from said feeding chamber into said plasma chamber; the plasma chamber and the feeding chamber being the same length and wherein the plasma chamber encloses the feeding chamber.
 20. A device for generating microwave plasmas, said device comprising: a microwave generator; a microwave feeding chamber of cylindrical design; a plasma chamber; a common wall between said feeding chamber and said plasma chamber; and a plurality of coupling points which are located within said wall and through which the microwave energy is conveyed from said feeding chamber into said plasma chamber; the plasma chamber and the feeding chamber being the same length, wherein said plasma chamber and said feeding chamber comprise end faces and wherein said microwave generator is arranged in or near one of said end faces or a wall of one of said chambers. 